OBJECTIVE: To associate exclusive breastfeeding
with central and peripheral adiposity measured by body mass index, waist and
arm circumferences, triceps and subscapular skinfolds and their sum in preschool
children.METHODS: This cross-sectional study
enrolled 134 preschool children aged 3-5 years from a private school in Brasília,
Brazil. All children had their body weight, height, waist and arm circumferences,
and triceps and subscapular skinfolds measured. Children's parents answered
a questionnaire about breastfeeding duration. Overweight and obesity were diagnosed
based on the World Health Organization's classification for the body mass
index for age.RESULTS: Girls had higher adiposity
in the triceps skinfold (p=0.001), subscapular skinfold (p=0.044)
and in their sum (p=0.003), when compared to boys. Prevalence of overweight
and obesity was similar between genders (25.4% for boys and 22.6% for girls),
as it was exclusive breastfeeding (4.3 months for boys and 4.6 months for girls).
A significant inverse correlation was found only between exclusive breastfeeding
and waist circumference (r=-0.166; p=0.05). Other anthropometric variables
showed a trend to present an inverse correlation with exclusive breastfeeding,
but lacked statistical significance. CONCLUSIONS: The significant inverse
association between exclusive breastfeeding and waist circumference indicates
a possible effect of breastfeeding in body fat distribution in preschool children.

The increase in childhood obesity over the past
two decades has raised a series of hypotheses regarding the reasons that trigger
this process. Setian et al(1) report that the development
of obesity could be caused by an imbalance between caloric intake and energy
expenditure, or be determined by genetic, pathophysiological (endocrinemetabolic),
environmental (eating habits and physical activity) and psychological factors.

In this regard, several studies have sought to
relate obesity with environmental variables that influence the lives of children.
Among these variables is breastfeeding, which, in addition to improving the
neurological, visual, and psychosocial development and protecting against various
morbidities(2), is mentioned as a protective factor against the development
of overweight and obesity in several studies(3-7).

The early diagnosis of overweight and obesity can
help prevent and combat excess weight and prevent the development of cardiovascular
disease and degenerative diseases associated with it, such as atherosclerosis,
glucose intolerance, diabetes mellitus type 2, dyslipidemia and hypertension(8).
The recent release of the new child growth standards, by the World Health Organization
(WHO), which include, along with weight and height, indicators such as arm circumference
and triceps and subscapular skinfolds(9), facilitates the diagnosis
and assessment of adiposity in children.

Thus, the present study is based on the assumption
that children exclusively breastfed for longer periods would have lower measures
of adiposity, considering the protective factor of breast milk against the development
of overweight and obesity(3-7). Therefore, the aim of the study was
to evaluate possible associations between the duration of children's exclusive
breastfeeding, body mass index (BMI) and central and peripheral adiposity, through
the waist and arms circumferences, triceps and subscapular skinfold, and the
sum of these measurements, in preschool children at a private school in Brasília,
Brazil.

Method

Sample consisted of 134 preschool children aged
between three and five years, enrolled in Centro Educacional Católica
de Brasília (CECB), a private school in Brasília, Brazil. The
school has about 3.500 students, 330 of which are aged between three and five
years, and is predominantly middle class and upper middle class, with classes
ranging from early childhood education until the end of high school.

In one single meeting (cross-sectional study),
the children were assessed for weight, height, waist circumference, arm circumference,
and triceps and subscapular skinfolds on the left side, according to the guidelines
proposed by the WHO standard(10). All children aged between three
and five years were invited to participate in the study, with the
precondition of parents answering a questionnaire including questions about
breastfeeding (exclusive and complementary) and signing an informed consent
form. The research was approved by the Ethics Committee for Research of Universidade
Católica de Brasília (UCB).

Body mass was measured using a Filizola scale (São
Paulo, Brazil), with 100g accuracy. Height was measured using a Gofeka stadiometer
(Santa Catarina, Brazil) with a 0.1cm accuracy. Arm and waist perimeters were
measured with a Cescorf® inextensible anthropometric measuring
tape (Rio Grande do Sul, Brazil) with 0.1cm accuracy. The measurement of waist
circumference was performed with the children in the upright position, at the
midpoint between the last rib and iliac crest. The subscapular and triceps skinfolds
were measured with a Lange skinfold caliper (Maryland, USA) with 0.5mm accuracy.
The triceps fold was measured at the midpoint between the olecranon and the
acromion of the left arm, and the subscapular fold just below the subscapularis
and inferior angle of left scapula.

Children were diagnosed as thin, normal, overweight
or obese, according to the z-scores recommended by the World Health Organization(11)
and enforced by the Ministry of Health, through the use of software Anthro
and Anthroplus.

Sample size was calculated according to the equation
to estimate samples in a finite population(12), and the confidence
level was set at 95%, which corresponds to a value of 1.96 expressed in standard
deviations numbers; the percentage by which the phenomenon takes place is fixed
at 16.6%, once the children included in the study could be exclusively breastfed
for one month until their six months of life; the total population for the analyzed
school was 330 students aged three to five years, and the sampling error was
set at 5%. According to this calculation, the necessary sample for this study
was 130 children.

For comparisons between anthropometric measurements
and the prevalence of overweight and obesity, according to sex, the Student's
t-test for independent samples was used. The Pearson correlation was used to
analyze the relationship between the duration of breastfeeding and the anthropometric
variables, using SPSS® 15.0 for Windows, and the degree of significance
was set at p<0.05. The power calculation was performed with the aid
of the G*Power

3.0.10 software, and it reached values of 0.81
for the mean comparison test and 0.95 for the correlation test.

Results

Of the 134 children studied, 71 were female and
63 male, 20.1% (n=27) were three years old, 37.3% (n=50) were four years old
and 42.5% (n=57) were five. Table 1 shows the general characteristics of children.
Student's T-test for independent samples indicated a significant difference
between sexes for the triceps skinfold (p=0.001), subscapular skinfold
(p=0.044) and for the sum of both skinfolds (p=0.003), with girls
showing greater adiposity than boys.

Overweight and obesity were identified in 23.8%
(n=32) of preschool children, with 25.4% (n=16) of cases affecting boys and
22.6% (n=16) affecting girls. Thinness was detected in only one child (0.7%).
There were no significant differences in the frequency of overweight between
the sexes and different age groups (Table 2).

Mean duration of breastfeeding was 4.5±1.6
months, without significant differences between the sexes. The frequency of
overweight in children who were exclusively breastfed until they were sixth
month old was 21.2%, whereas for those who were exclusive breastfed until their
second month of life, the rate was 26.7%. The Pearson correlation between duration
of children's breastfeeding and the anthropometric variables assessed
showed an inverse association with all variables. The correlation was significant
regarding waist circumference (r=-0.166; p=0.05), as shown in Table 3
and Figure 1.

Discussion

Numerous studies have associated the time of exclusive
breastfeeding and the development of overweight and obesity. Particularly noteworthy
are the studies by Siqueira and Monteiro(3) Victora et al(4),
Koletzko et al(5), Harder et al(6), Shields
et al(7) Von Kries et al(13) and Gillman
et al(14), which have found a dependent effect between the
duration of breastfeeding and the incidence of overweight and obesity in children
and adolescents. Bergmann et al(15) have observed statistically
higher values for subscapular and triceps skinfolds in artificially fed children.

Review studies and meta-analysis have also raised
evidence that prolonged breastfeeding is associated with lower prevalence of
obesity and a lower BMI compared to children and adolescents who consumed milk
formula(2,16,17). Owen et al(18) have associated
breastfeeding with low levels of insulin, preprandial blood glucose, pre- and
postprandial insulin, and an approximately 40% lower risk of developing type
2 diabetes mellitus. Martin et al(19) reported an inverse
association between breastfeeding and high blood pressure.

Moreover, the literature also shows studies that
have found no association between breastfeeding and overweight. Li et al(20)
have found no protective effect of breastfeeding on the development of
obesity. Kramer et al(21) have found no beneficial effects
of prolonged exclusive breastfeeding on blood pressure, height, BMI, waist circumference,
triceps and subscapular skinfolds. Burdette et al(22) have
found no statistically significant results when comparing body fat through Dual-Energy
X-Ray Absorptiometry (DEXA), with duration of breastfeeding or introduction
of complementary feeding.

An inherent limitation of our study may have been
the quantification of exclusive breastfeeding time through the use of questionnaires,
which could lead to a bias of neglect by parents. Other studies in the literature,
however, report the collection of this data by using the same instrument(14,20).
Additionally, our cross-sectional survey only allows for assessment of the degree
of adiposity at a given time in the lives of children, thus suggesting the need
for longitudinal studies in order to better monitor the growth and development
of these children.

This study shows a trend toward a lower incidence
of overweight and obesity in preschool children who were breastfed exclusively
until the sixth month of life. Furthermore, we observed a significant inverse
correlation between waist circumference and duration of breastfeeding. This
result was also observed by Rudnick et al(23), in which individuals
who were breastfed for more than a month had lower waist circumference, lower
waist-hip ratio, and a 15% lower risk of developing obesity, in addition to
lower levels of inflammatory markers when compared to those breastfed for less
than 30 days.

The importance of this finding is due to the
known effect of visceral adiposity as a predisposing factor for developing chronic
diseases such as arterial hypertension, dyslipidemia, metabolic syndrome, type
2 diabetes mellitus, and others(2429). This finding highlights a
possible effect of breastfeeding on body fat distribution in childhood.